The Environmental Protection Agency requires that an aircraft water system be sanitized and inspected on a scheduled basis. Therefore, in order to meet these requirements, systems for disinfecting and sanitizing the water on an aircraft have been developed. Many of these systems include the use of caustic chemicals and are only as effective as the technician performing the tasks required.
One system uses a clean and purge process using chlorine or chlorine dioxide. While cleaning the water system with chlorine disinfects the potable water, it also has several disadvantages. The chlorine may cause corrosion to the water system's equipment and produces the carcinogen trihalomethane (THM) which may remain in the potable water supply after cleaning. Furthermore, chlorine does not break down bio-film on the water system's equipment below a concentration of 50 parts per million, and it only minimally inhibits bio-film from reforming on the water system's equipment.
The use of chlorine dioxide eliminates some of the problems associated with cleaning and purging with chlorine. Chlorine dioxide does not produce the carcinogenic THMs associated with the use of chlorine. Chlorine dioxide also breaks down bio-film and can inhibit reformation of bio-film on the water system's equipment. However, the use of chlorine dioxide to clean the water system can still lead to corrosion of the water system's equipment. Additionally, the use of both chlorine and chlorine dioxide is time consuming and is only as effective as the technician carrying out the process.
Another option is to clean the water system using copper-silver ionization. This process leaves minimal deposits of copper on the water system's equipment and causes no corrosion of the equipment. However, copper is toxic to aquatic species and depending on the concentration of the chemical, it will not break down bio-film or inhibit its reformation.
Ultra-violet (UV) radiation or a combination of UV radiation and chlorine can also be used to clean the water system. The use of UV radiation eliminates the use of a chemical, has no impact on the water system's equipment, and no adverse environmental or health effects. UV radiation, however, does not break down bio-film or prevent it from reforming on the water systems equipment. UV radiation, with the addition of chlorine, breaks down bio-film at concentrations above 50 parts per million, but has little effect on the reformation of the bio-film after cleaning. The addition of the chlorine also introduces the problems of possible corrosion of the water system's equipment and the inclusion of the carcinogen THM in the potable water. These and other disadvantages exist with known systems.